1. Field of the Invention
The present invention relates to a developing method of a photoresist which is part of a photolithographic technology utilized for the manufacture of semiconductors and a developing device, and in particular, to a developing method of a photoresist in which a photoresist having adhesion can be surely removed even in the case where the photoresist is formed on a substrate having a pattern including concavities and convexities, and a developing device for implementing the developing method.
2. Description of Related Art
A solid-state image pickup device, such as a CCD and a CMOS imager, which is a type of semiconductor devices, is utilized in a variety of fields. The solid-state image pickup device comprises circuits such as a light receiving part made of a photodiode, a read-out part for reading out electrical signals on the basis of the output of the light receiving part, or the like. The solid-state image pickup device is manufactured by layering a plurality of layers on a semiconductor wafer, using a photolithographic technology which, itself, is well known.
In recent years, an increase in the density, an increase in the resolution and miniaturization of the solid-state image pickup device have been in demand, and the size of the pitch per pixel has tended to be smaller. In order to satisfy this demand, the area of the light receiving part (hereinafter referred to as a light receiving region) must be reduced. In the case where a light receiving region is reduced, the amount of received light is reduced, and the dynamic range is reduced, and therefore, it is necessary to compensate for the reduction in the amount of received light by arranging micro-lenses on the light receiving part.
Generally, micro-lenses are formed by processing a transparent resin into lens form, on the surface of a semiconductor chip where a functional element for a solid-state image pickup device has been formed. Accordingly, the surface of the solid-state image pickup device is in a pattern including concavities and convexities, due to micro-lenses. The light receiving surface of the solid-state image pickup device is extremely important for a sensor, and in the case where a foreign substance adheres to the light receiving surface, the level of reproduction of the picked up image is lowered, due to a change in the brightness and color tone caused by the foreign substance, and there is a risk that the light receiving surface may be scratched. Thus, the quality and reliability of the solid-state image pickup device are damaged by adherent foreign substances, and therefore, the light receiving surface of the solid-state image pickup device is protected with a transparent lid, such glass etc., so that no foreign substance adheres to the light receiving surface.
As described above, a solid-state image pickup device has a structure where the light receiving surface is protected by a lid, and in particularly, the surface of the solid-state image pickup device where micro-lenses are formed on the chip is in extremely complicated form including concavities and convexities. Therefore, the light receiving surface is covered with the lid after mounting the semiconductor chip in a package case, such as ceramics, plastic etc., and the solid-state image pickup device has a structure where no foreign substance can enter from the outside, in the state where the solid-state image pickup element is protected within the package case. However, miniaturization of the structure of the solid-state image pickup device mounted in a package is limited, and therefore, as shown in FIG. 1, a structure has been proposed, where glass 106 adheres with an adhesive 105 by the use of an epoxy resin sheet 104 having a hollow portion 103 only above a light receiving part 102 to the surface of a semiconductor chip 101 where a solid-state image pickup element has been formed (see, for example, Japanese Patent Application Laid-Open No. 2001-257334). Thus, the glass 106 (lid) directly adheres to the semiconductor chip 101, thereby miniaturizing the solid-state image pickup device, as compared to the solid-state image pickup device mounted in a package.
In order to manufacture a solid-state image pickup device as described above, however, the epoxy resin sheet 104 is used in order to secure a space between the glass plate 106 and the semiconductor chip 101, and the glass plate 106 adheres to the semiconductor chip 101 by applying the adhesive 105 on the both surfaces of the epoxy resin sheet 104. A hole is formed in the epoxy resin sheet 104 so that the sheet is not placed on the light receiving part 102. Therefore, tension applied to the sheet becomes uneven, due to the effect of the hole, and there is a problem that an adhering process is highly difficult by the extremely unstable form of the epoxy resin sheet 104 when the epoxy resin sheet 104 adheres. In addition, in the case where the epoxy resin sheet 104 adheres to the surface of the semiconductor chip 101, time and effort are needed to position the epoxy resin sheet 104 relative to the semiconductor chip 101, and the measure for preventing pollution on the light receiving surface on which micro-lenses are placed is insufficient, and therefore, a problem arises where management of the manufacturing process is complicated.
In addition, the hollow portion 103 is formed in the epoxy resin sheet 104 through a process for forming a hole, and therefore, there is a limit to the miniaturization of the hollow portion 103. The size of the sealed space of the solid-state image pickup device is determined by the hollow portion 103, and therefore, there is a limit to the miniaturization of the structure of a solid-state image pickup device, even in the case where the method disclosed in Japanese Patent Application Laid-Open No. 2001-257334 is used.
In addition, in development of a photoresist used in a semiconductor process or the like, in the case where the surface of a substrate on which the photoresist is formed has concavities and convexities, it is easy for the photoresist to remain as residue in portions from which the photoresist must be removed. Though the surface of a semiconductor wafer formed a semiconductor element usually has a structure including concavities and convexities, particularly in the case of a semiconductor wafer formed a solid-state image pickup element, residue of the photoresist on top of the light receiving part sometimes causes defects.